title: An N-end rule destabilization mutant reveals pre-Golgi requirements for Sec7p in yeast membrane traffic.
abstract: Sec7 protein (Sec7p) is required for membrane traffic in the yeast secretory pathway. Because Sec7p regulates more than one stage in the pathway, it has been difficult to assign the most proximal requirement for Sec7p action. We have engineered a novel mutant whose Sec7p levels are regulated by growth conditions and by selective protein destabilization according to the N-end rule. Sec7p depletion causes cell growth arrest and accumulation of transport proteins with post-translational modifications indicative of Sec7p dependence for ER-to-Golgi traffic, in addition to the already characterized Golgi requirements. Immuno-EM of sec7 revealed exaggeration of ER and Golgi membranes with protein accumulation in these exaggerated structures, suggesting that these regions may represent staging areas for cargo sorting and vesicle assembly.
authors.affiliation: Department of Cellular & Structural Biology, University of Colorado Health Sciences Center, Denver 89262, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wolf
authors.forename: M
authors.initials: M
authors.lastname: Nicks
authors.forename: S
authors.initials: S
authors.lastname: Deitz
authors.forename: E
authors.initials: E
authors.lastname: van Tuinen
authors.forename: A
authors.initials: A
authors.lastname: Franzusoff
mesh_terms: D001693:Biological Transport, Active; D002268:Carboxypeptidases / Q000378:metabolism; D043402:Cathepsin A; D002455:Cell Division; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D005800:Genes, Fungal; D005818:Genetic Engineering; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D020662:Guanine Nucleotide Exchange Factors; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D005656:Fungal Proteins; C066709:GAS1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D008562:Membrane Glycoproteins; D029701:Saccharomyces cerevisiae Proteins; C066755:Sec7 guanine nucleotide exchange factors; D002268:Carboxypeptidases; D043402:Cathepsin A